I'll mention two more choices... Roadtrek makes a 19' class B with Quigley's IFS 4x4 system installed on the Chevy Express 3500 van. They suggest limiting it to beaches and snow.
I don't know if Xplorer is still in business. They made fine class B's under the original owner, but have been thru a few owners since. Last time I looked at the website, they had had the same stuff up for at least 5 years, and some of it was obvious Photoshopped 'we could build this' type stuff. I did see one of their F450 or F550 4x4 C's on a used RV lot about 7-8 years ago. The lot owner had taken it on a 1,000 mile trip, and said it was a gas hog and rode very poorly.
Jim, "Be careful reading the fine print. There's no way you're going to like it."